This invention relates to materials and methods for screening chemical compounds for potential pharmaceutical activity, and more specifically to an electronically-indexed solid phase assay using transponders embedded in the solid phase particles.
Methods of solid-phase chemical synthesis have been widely used in drug discovery. Their advantages include the ease of separating compounds synthesized on the solid phase from the substrates and byproducts of the reactions by centrifugation, filtration, magnetic separation, gravity and others, and the ease of handling and assaying the compounds after the synthesis. Compounds immobilized on the solid phase can be subjected readily to a variety of assays, including immunoassays.
Many classes of compounds have been successfully synthesized using solid-phase methods, including peptides, oligonucleotides and small molecules. There are two general types of compounds that can be synthesized in a combinatorial fashion, linear polymers consisting of one or more monomeric building blocks, e.g. peptides, and compounds built on a small-molecule scaffold. In the latter case the structure of the molecule with regard to the position of the building block can be considered xe2x80x9cbranched.xe2x80x9d The latter case is exemplified by compounds from the benzadiazepine family. Hybrid approaches are also possible, where the compounds have a branched structure, but each branch is composed of a linear chain of building blocks, or vice versa.
In existing solid-phase chemical synthesis methods the solid phase is a passive vehicle. The main utility of the solid phase is to aid in separating the desired product or intermediate of the reaction from the substrate and byproducts.
Conventional methods for identification of the synthesized compound are limited because the amount of the compound needed for full characterization (often 1 mg) is much more than the quantity that can be released from a single solid phase particle. One way to overcome this problem is to tag the particle with a biomolecule during the course of the synthesis by co-synthesizing this biomolecule together with the compound of interest. Examples include the co-synthesis of a nucleic acid for peptide combinatorial libraries, the use of halogenated derivatives of carboxylic acids, or the co-synthesis of peptides as tags for small molecules. This method also has limitations, however, in that the chemistry of the synthesis of small molecules may be incompatible with the chemistry of molecular encoding. Additionally, using a molecular tag can double the number of synthetic steps involved in the process.
This invention overcomes many of these problems by employing transponders embedded in the particles used as the solid phase. Thus, each individual solid phase particle can be assigned a unique index number, electronically encoded inside the particle, that can be recovered at will at any time after the synthesis is complete, thus enabling the identification of the compound on the bead.
According to the present invention, the solid phase performs an additional function, i.e. storage of the information about the progress of the chemical synthesis in an electronic memory element inside the solid-phase particle, or bead. The contents of the memory can be retrieved by a dedicated scanner device at a desired time after the synthesis is completed, or at multiple times during the synthesis, or monitored continuously during an assay. In the combinatorial chemical synthesis methods of this invention, the solid-phase particles are derivatized with a chemical scaffold, or support, on which synthetic condensations are conducted.
Following combinatorial synthesis, the pool of derivatized particles can be exposed to a target protein of pharmaceutical interest to investigate which particles carry compounds that bind to the target protein, using immunoassay techniques. The particle can also be a source of a small quantity of the compound of interest for identification purposes. The identified compounds can be re-synthesized and subjected to further phases of drug development.
In one aspect, the present invention provides a particle for use in solid phase chemical synthesis, wherein a transponder is embedded in the particle.
In a second aspect, the present invention provides methods of solid phase chemical synthesis employing an electronically indexed solid phase.